Re: SETLL *START and %EQUAL

Hi Alan,

If the question became "Equal to what, exactly?", I would say equal to the key in the *START (or first) record.

I don't like it, but I can accept that %equal is only *ON if a particular key was specified and it exists. But in my mind, when I say "SETLL *START MyFile;" I'm specifying the key of the starting record in the file, and if the file is not empty, there must be a starting record.

Similarly with %found, why would it be *OFF if a record exists in the file?  "SETLL *START MyFile;": couldn't find anything in a non-empty file? The manual actually says

"The resulting indicators reflect the status of the operation. You can specify an indicator in positions 71-72 that is set on when the search argument is greater than the highest key or relative record number in the file. This information can also be obtained from the %FOUND built-in function, which returns '0' if no record is found, and '1' if a record is found."

which is not accurate when using SETLL *START.




On 3/17/2023 3:30 AM, Alan Cassidy wrote:

I would rephrase Jon's explanation this way.

When you use SETLL using the key field values for the file you're reading, you get %equal = '1' if it finds a record with keys that match those values. If you key field "valules" is *START, you aren't giving the statement any arguments to match against the key fields. "Whatever you get" is meaningless, because the question becomes, "Equal to what, exactly?"

--Alan Cassidy


On 3/16/2023 6:21 PM, Jon Paris wrote:

I don't think $equal should be set here as it used to indicate that it detected a record in the file with a key equal to that of the value specified. But no valid key was specified!

Remember that SETLL is attempting to position the read cursor _before_ the first record with the desired key. Telling you that it was able to exactly match (i.e. %equal) is basically just a useful courtesy. If you think of it that way the failure to set %equal may make more sense.

As to the second part of your question, I'm not sure where it is documented - but as a general rule parens mean "this key may not be in the exact right format - please deal with it." - so a packed number will be accepted for a zoned key for example.  In the case of *Start they are meaningless.

    Jon P.

On Mar 16, 2023, at 5:19 PM, Peter Dow <petercdow@xxxxxxxxx> wrote:

I have a program that has

  SETLL *START MyFile;
  IF %EQUAL();
        READ MyFile;
  ELSE;
       do something different;
  ENDIF;

In debug, I discovered that it does something different. My first thought was that maybe it's because the file is empty, but it wasn't.

After reading the manual, the closest thing I can see to saying why %EQUAL was *OFF was this:

"You can specify an indicator in positions 75-76 that is set on when a record is present whose key or relative record number is equal to the search argument. This information can also be obtained from the %EQUAL built-in function, which returns '1' if an exact match is found."

I guess there's an argument to be made that *START is not an exact match with whatever is in the first record, but one could also say that the first record is always a match for the first record.

I also noticed that the manual does not say what the effect of () around the search argument is.  My assumption there is that the () define a list of values that are converted to match the related key fields, but the manual does not say that.

Where is this stuff actually stated?

--
*Peter Dow* /
Dow Software Services, Inc.
909 793-9050
petercdow@xxxxxxxxx
pdow@xxxxxxxxxxxxxx

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